Apparatus and method for determining the page description language in which a print job is written

Abstract: There is provided a printing system for producing prints from a print job written in one of a plurality of page description languages with the print job assuming the form of a print job stream (20). The printing system includes a plurality of page description language analyzing units (202) for sampling the print job stream, each analyzing unit outputting an information signal (I 0 ....I n ) which provides information regarding the print job stream. A filter (204), which receives the information signals, processes the information signals and outputs a filtered signal which indicates the page description language in which the print job is written.

Description: The present invention relates generally to a printing system and, more particularly, to a technique which facilitates the interpretation of a print job written in a page description language by determining the page description language in which the print job is written. Personal computers have become commonplace on the desks of most office workers. Typically, much of the work product of such computers is intended to be transformed into hardcopy via a printer using digital imaging technology. Xerox® Corporation presently is marketing a server for a printing apparatus, the server being referred to as the DocuTech® Network Server ("DocuTech Network Server" is a trademark of Xerox Corp.) This server is adapted to translate a job written in a first page description language ("PDL"), such as Postscript® ("PS") or Hewlett Packard Printer Control Language ("HP-PCL"), into a second PDL, such as Interpress, for printing of the job on a Xerox® compatible printing apparatus. At the heart of the server are two interpreters, one of which is adapted to translate PS and the other of which is adapted to translate HP-PCL. Each interpreter contains software, written by either Adobe® Systems Inc. or Peerless® Corp. to facilitate the translation process. A PDL is a method of describing printed page(s) in a printer independent format. A PDL establishes an interface between a print driver or client and a print server or printer. The following references are pertinent to the area of page description languages: PostScript® Language Reference Manual Second Edition Addison-Wesley Publishing Co. 1990 PCL 5 Printer Language Technical Reference Manual First Edition Hewlett Packard Co. 1990 As is noted in art cited above, the control of, and software for, printers in a system or network environment can be in the printer itself. Commonly, however, a major part of the system printer integration software operation may be in the print server connected into the system, (typically a stand alone but dedicated small computer or PC). The server typically functions as a "spooler" to buffer the jobs that are sent to it, as well as a page description language (PDL) "decomposer", for converting the PDL files (e.g., "Interpress™" or "PostScript®") to bitmapped files for application to the printer. The electronic printing standard includes a specific set of instructions for printing in a standard for representing documents digitally. The Interpress™ standard for representing printed pages is supported by a wide range of Xerox® Corporation other products. The print service understands and processes Interpress™ instructions received from a workstation, transforming them into a format understood by the printer. Each page of an "Interpress™" master can be interpreted independently of others. This allows a user to easily produce new masters from existing ones and allows the printer to selectively print pages from any master it receives. Although a "formatting print service" may not have a printer directly attached, it can perform much the same as a print service that does. The typical principal difference is the transferring of an Interpress™ master into an internal format understood by the printer. The formatting print service creates a secondary Interpress™ master which accurately represents the same image but in a subset of Interpress™ which can be directly processed by the designated or target printer. This secondary Interpress™ master is then transmitted to the formatting print service's target printer for processing and printing. Workstations on the network with conversion software can interact with the print service. This software runs automatically when users request that a document be printed. It converts the document format used by the workstation into an Interpress™ master which is transmitted to the print service. This transfer is implemented by a network queuing subsystem which implements the printing protocol and interfaces with an internal print queue for the tracking of the Interpress™ master. The user can see the status of a print job and its place in the queue by making a request through the print server terminal or at the workstation. Once the document has been printed, the print service can delete the Interpress™ master. In US-A-5,226,112, a print job is transmitted from a client workstation to a print server in which a host processor is coupled with a coprocessor, the coprocessor including an interpreter for translating the incoming PDL to a PDL which is compatible with one or more available printers. If the interpreter in the coprocessor is unable to translate the incoming PDL, then the host processor causes the interpreter to be swapped with a stored interpreter, the stored interpreter being suited to translate the incoming PDL. EP-A-0558804 (cited under Articles 54(3) and (4) EPC) refers to a printing system responsive to a plurality of input languages in which the language of an incoming block of data is identified by analyzing both syntax and context. The language identification procedure includes a plurality of voter modules, each of which is specifically assigned to the analysis of an expected printer language. A decider module receives outputs from each of the voter modules and decides, based upon those voter module inputs, the most likely identity of the received language. The decider then instructs a processing unit to access a syntactical decoding software that will enable it to interpret and execute the decided-upon language. WO-A-9204672 describes a method and system for matching the software command language of a computer with a printer language, wherein the nature, character and frequency of a stream of data generated from computer software is sensed to determine the particular language in which the computer is operating. For sensing, a plurality of character counters is included, and based upon their output, a comparator decides whether or not sufficient data have sensed to facilitate a language determination by a subsequent language determinator stage. EP-A-0332779 relates to a printing system in which a control code judging unit selects, dependent on data held in an input data buffer, a respective one of a plurality of code groups. The selection is made by making a comparison between the data in the data buffer and the groups of character control codes in a weighting manner obtaining numeric values expressing the probability that the given data falls within each specific code group. Finally, the group from which the maximum numerical value is obtained is selected. EP-A-0469974 refers to a printer which comprises a microprocessor with a resident algorithm and a plurality of data sets, obtained by statistical techniques, stored therein for analyzing a captured portion of an input data stream to identify the printer control language in which the data stream is written. The characterizing data sets comprise statistical data reflecting the likelihood of short sequences of characters occurring individually or in combination in print jobs encoded in a given printer control language. It is an object of the present invention to provide an improved system and method for determining the page description language in which a print job is written. This object is solved by the subject matter of the independent claims. Preferred embodiments of the present invention are defined by dependent claims. In accordance with a preferred embodiment of the present invention there is provided a printing system for producing prints from a print job written in one of a plurality of page description languages with the print job assuming the form of a print job stream, including: a plurality of page description language analyzing units for sampling the print job stream, each analyzing unit outputting an information signal which provides information regarding the print job stream; and a filter, receiving each of the information signals, for processing the information signals and outputting a filtered signal which indicates the page description language in which the print job is written. A printing system in accordance with a preferred embodiment of the invention may further comprise a print server for interpreting the page description language of the print job to prepare the print job for printing. Said plurality of page description analyzing units and said filter may be operatively associated with said print server. The filter may be programmable and may include criteria for the processing of the information signals with one of the criteria being programmed by said server. A printing system in accordance with a preferred embodiment of the invention may further comprise an input source for generating the print job and transmitting the print job stream to said plurality of page description language units. The filter may be programmable and may include criteria for the processing of the information signals, wherein said input source includes means for over-riding one of the criteria. In accordance with an preferred embodiment of the invention, there is provided a printing system in which the print job stream includes a plurality of operators representative of the page description language in which the print job is written and sets of selected operators follow a distribution, wherein a certainty factor, varying as a function of the distribution, is outputted from one of said page description language analyzing units. An embodiment of the invention comprises a system in which the page description language of the print job can be one of a plurality of versions, wherein the certainty factor varies as a function of which page description language version the print job assumes. In accordance with a preferred embodiment of the present invention, there is further provided a method of determining a page description language in which a print job is written with the print job being written in one of a plurality of page description languages and assuming the form of a print job stream, comprising the steps of communicating the print job stream to a plurality of page description language analyzing units; generating a plurality of information signals from the plurality of page description language analyzing units, each of the information signals providing information regarding the print job stream; transmitting the information signals to a filter; and processing the information signals with the filter for generating a filtered signal that indicates the page description language in which the print job is written. A method in accordance with the invention may further comprise the step of transmitting the filtered signal to a print job translating unit which translates the page description language of the print job into another page description language. By way of example only, an embodiment of the invention will be described with reference to the accompanying drawings, in which: Figure 1 is a schematic view of a printing system including a plurality of client workstations interfaced with a printer by a print server; Figure 2 is a schematic view of a job file and the contents thereof; Figure 3 is a representation of a format for an electronic job ticket; Figure 4 is a schematic, block diagrammatic view of the printer and print server; Figure 5 is a schematic view of a memory map to interpret a page description language; Figure 6 is block diagram depicting an arrangement for analyzing a print job stream and determining the page description language in which the corresponding print job is written; Figure 7 is a flow diagram illustrating an implementation for use with the analyzing arrangement of Figure 6: and Figure 8 is a graphic representation of a sample distribution outputted by an analyzing unit of Figure 6. Referring to Figure 1, there is shown a printing arrangement, designated generally by the numeral 10. The printing arrangement 10 includes a plurality of remote inputs such as PCs, workstations, etc. (referred to herein as workstations 14), coupled via one or more networks 20 to a server 25. Workstations 14 include a CRT type display screen 15 together with keyboard and mouse for entering programming instructions, image data, etc. Screen 15, which may be a touchscreen, displays various job program choices, operator instructions, messages, etc. The server 25 is, in turn, coupled through one or more networks 28 to one or more printing systems 35. While separate networks 20, 28 are shown, a single network may instead be used. Referring to Figure 2, electronic job files 60, or parts thereof, are created at the individual workstations 14, each job file being comprised of a Job Specification 62 and Print Data file 63 expressed in a PDL. Job Specification 62 is in the form of a client server job ticket 64 having instructions for routing, handling, and processing the job 62. As will be clarified from the discussion below, in the preferred embodiment of the present invention, the PDL of print data file 63 is either written in Postscript® ("PS") or Hewlett Packard Printer Control Language ("HP-PCL"). The jobs in Print Data file 63 are electronic in form, consisting of image signals or pixels generated, for example, by scanning hard copy documents and converting the document images to image signals or pixels, directly by a keyboard, taken from memory, or consisting of page format and/or graphic output commands all encoded in one of the preferred PDL encodings. The content of the job files are normally compressed to increase bandwidth and reduce the amount of storage required. The image signals, pixels or PDL instructions in Print Data File 63 are arranged as electronic documents or pages for printing on a print media such as paper stock or sheets. The programming instructions in the client server job ticket 64 accompanying the job file 60 may include selection of the printer in the case where plural printers are available for the client or user to choose from in printing system 35. Where a printing system 35 has printers with different features, functions, speeds, etc., it may be necessary that the client select the printer that is to be used initially so that a client server job ticket 64 with the program selections available with that printer may be displayed at the client's workstation 14 as described more fully in EP-A-0,529,818. During the printing process, the server 25 transmits the printing instructions from the client server job ticket 64 to the printing system selected. Referring to Figure 3, the client server job ticket 64 may assume an ASCII format. Additionally, by employment of suitable client UI interface dialog software, print job selections may be displayed on the display screen 15 so that the user can be apprised of which printing selections are available for programming a print job. Examples of client server job ticket displays are shown in U. S. Patent No. 5,226,112. The client at the workstation interactively fills out the client server job ticket by making selections electronically using the workstation mouse, keyboard, etc. It should be recognized that the client server job ticket instructions encompass not only print programming instructions for the job itself but also routing and handling instructions for the server 25. The completed client server job ticket 64 is combined with the job in Print Data file 63 in the job file 60. The client server job ticket includes information regarding a print file specification for the job file 60. In the illustrated embodiment of Figure 3, the print file specification is designated with the parameters: "%XRXsourceFile" and "%XRXdestination". The significance of the print file specification to the present description will be discussed in further detail below. The server 25 comprises any suitable interface for receiving job files 60 from workstations via network 20, with the ability to access and decode the job processing instructions on the accompanying client server job ticket. The server 25 preferably includes an on-board memory of suitable capacity for temporarily storing the job files pending processing thereof by printing system 35. The print manager on-board memory may be large enough to support long term storage of the job files or parts of the job files. Alternatively, one or more remote memories 42 (Figure 1) may be provided for this purpose. The printing system 35 may include one or more high speed electronic printers 50 for processing jobs in accordance with the instructions input through the client server job ticket accompanying each job file. While a single printer 50 is shown, plural printers, either at a single central location or at several remote locations may be envisioned. Printer 50, for example, may be a xerographic based printer of the type shown and described in U. S. Patent No. 5,170,340. In other contemplated implementations of the preferred embodiment, the printer 50 could comprise other known printer types such as ink jet, ionographic, LED, and the like. Referring to Figure 4, the structure of the server 25 and the printing system 35 is discussed in further detail. In the preferred embodiment of the invention, a swapping technique is achieved with an arrangement that is designated by the numeral 70. The software used to operate the arrangement 70 is hereinafter referred to as the "print service application". The arrangement includes a host processor 72, an accelerator coprocessor (ACP) card 74 and a disk storage device 76. In one example, the host processor is an IBM PC-AT system having an Industry Standard Architecture (ISA) or an Extended Industry Standard Architecture (EISA) bus to accept the ACP card. The host processor 72 can be configured for operation in a network environment. When the host processor 72 is configured for network operation, it is preferably Novell® certified for Netware 386™. In the preferred embodiment, the ACP card 74 comprises the following major blocks: 80960CA Microprocessor Host System ISA Interface Extended Bus Interface Memory (16 MBytes) Programmable Read Only Memory Timer/Counter 256 Byte Board Identification EEPROM The host processor 72 is capable of transferring data to and from ACP memory through a 128K byte sliding shared memory window. The ACP 74 also can use a small section of the host processor's IO address space. By writing to an 10 data port of the ACP 74, the host processor 72 is able to send commands to the ACP 74. In turn, by reading the IO data port, the host processor 72 is able to receive acknowledgement messages back from the ACP 74. These messages are typically 1 byte in length and are used to synchronize the actual data transfers in shared memory. In the preferred embodiment, two 8 bit data ports are used to communicate synchronizing swap requests and acknowledgements between the ACP 74 and the host processor 72 prior to the actual transfer of PDL decomposer code and font cache data. These two ports are referred to as: the Host to Processor and Processor to Host Data Registers ("HPDR" and "PHDR"). Referring still to Figure 4, the ACP card 74 is shown with a memory map 78-1, which memory map 78-1 includes all of the software necessary to interpret a page description language, and the 80960CA microprocessor, the microprocessor being designated by the numeral 80. Referring to Figure 5, the memory map 78-1, which includes a user section 82 and a system section 84, is shown in greater detail. The memory map 78-1 further includes a section 86 having registers through which the HPDR and the PHDR can communicate and a status flag can be set. In the illustrated embodiment of Figure 5, the user section 82 comprises a section for retaining PDL interpretation code, the PDL interpretation code being adapted to facilitate the interpretation of a job file expressed in a first PDL, such as PS or HP-PCL. In the preferred embodiment, the PDL interpretation code is written by either Adobe® Systems Inc. or Peerless®. Corp., in conjunction with Xerox® Corp., for use by Xerox® Corp. in its Xerox Production Print Services System ("Xerox Production Print Services" is a trademark of Xerox® Corp.), the Xerox Production Print Services System preferably including a Media Server and a Network Server. It should be understood that the PDL interpretation code facilitates translation of the job file 60 from a first PDL, such as PS or HP-PCL, into a second PDL file, such as Interpress. Those skilled in the art will appreciate that such translation could be, in one example, achieved by using a configurable PDL interpreter, such as one manufactured by Adobe® Systems Inc. or Peerless® Corp to reduce the text and graphics of the job file 60 into a bitmap and then to express the bitmap in the form of a second PDL, such as Interpress. It should be appreciated that only selected portions of the system section 84 are shown. It will be recognized by those skilled in the art that, in practice, various software tools, such as tables, e.g., fault, system procedure and control tables, timers and controls therefor, control implementations, storage locations, and stacks, typically would be employed in the implementation of the system section 84. Referring to Figures 4 and 5, the microprocessor 80 includes a section 90 which contains information regarding the internal state of the microprocessor 80, such information including 1K memory, registers and states. This information selectively can be stored in a layer 92 of the system section 84. Referring specifically to Figure 4, the host processor 72 is coupled with the disk drive device 76 so that, as explained in further detail below, portions of the memory map 78-1 can be transferred, in the form of a context file, thereto. Preferably, at any one moment, one or more PDL context files, designated by the numeral 94, are stored in the disk drive 76. Upon processing a job file 60, the interpreted PDL file can be transmitted to one of a plurality of output or printing devices. In the preferred embodiment, the interpreted PDL file is expressed in Interpress, and is transmitted to the printer 50 which comprises a decomposer 96 and an image output terminal (IOT) 98. In one example, the decomposer 96 is of the type used in a Xerox® 4045 ("Xerox 4045" is a trademark used by Xerox®) printer and employs software of the type described in Interpress: The Source Book. Additionally, the IOT can be any suitable print engine, such as the DocuTech™ print engine mentioned above. In operating the printer, the interpreted output from the host processor 72 is transmitted to the decomposer 96 where it is decomposed into graphics and text for printing by the IOT 98. Further details regarding the swapping technique implemented with the arrangement 70 are discussed in US-A-5,226,112. Referring to Figures 4 and 6, an arrangement for determining the PDL of a print job, transmitted from one of the workstations 14 to the arrangement 70, is designated by the numeral 200. In the illustrated embodiment of Figure 6, the content of one of the network buses 20, i. e. the content of a PDL stream, is scanned by various PDL analyzing units 202-1, 202-2, 202-3, ... 202-N (hereinafter referred to conjunctively as "PDL analyzing units 202"). As is known, each print job assumes the form of a stream which is expressed in a PDL, the PDL representing image data and instructions for the print job. In the preferred embodiment, each PDL analyzing unit is capable of analyzing one or more PDL types. The PDL types may comprise, among others, PCL, PS, Interpress and TIFF. Preferably, one of the PDL analyzing units 202 is a binary filter which is used in conjunction with an arbiter, as explained in further detail below. As will be appreciated by those skilled in the art, the PDL analyzing units comprise a modular system and units can be added or deleted in accordance with the demands of the printing system 10. For convenience of discussion, the PDL determining arrangement is shown with only one of network buses 20, but, in practice, the arrangement 200 would be used with multiple buses. Additionally, the arrangement 200 is shown as a multi-tasking model in which the stream is sampled in parallel, but in other embodiments, the stream could be sampled with a pipeline model, i. e. in sequence, without affecting the concept upon which the disclosed embodiment is based. Finally, while the arrangement 200 is shown as being part of the arrangement 70, the arrangement 200 could be a service separate from the arrangement 70. In one preferred embodiment, each of the PDL analyzing units is a processor upon which software, suitable for analyzing the print job stream, is implemented. In another embodiment, the PDL analyzing units could be implemented in a multi-tasking system. As the print job stream is analyzed by the units 202, the latter transmit information signals I 0 , I 1 , I 2 , ... I N , respectively, to an arbiter 204. In one example, the arbiter (or "best guess arbiter") is a logical device or redundancy filter which is adapted to resolve ambiguities and set precedents. The arbiter 204, is preferably implemented with a combination of hardware and software, and is programmable. In the preferred embodiment, the arbiter communicates with various inputs other than the information signals. These other inputs, the significance of which will be described in further detail below, include a "client" signal, a "client rules" signal, a "client over-ride" signal, a "server rules" signal and a "server over-ride" signal. The primary purpose of the arbiter is to process the information signals for outputting a signal indicating the PDL of the print job stream. As shown in Figure 6, that output signal is transmitted from the arbiter 204 to the host processor 72. Referring to Figure 7, a discussion regarding the implementation of the PDL determining arrangement 200 is provided. In step 208 the print job stream is communicated to the PDL analyzing units 202. Some PDLs are recognized by their "signatures" while other PDLs are recognized by the frequency of occurrence of certain "operators". An example of a PDL characterized by a signature is Interpress, while a PDL characterized by the frequent occurrence of certain operators is PS. An example of an Interpress signature, as discussed in the above-mentioned "Interpress: The Source Book", is a "header" portion. In step 210, each unit examines the stream to determine if a signature is present. If a signature is present, then the PDL signature is translated into an information signal and transmitted to the arbiter 204 via step 220. For any units without a signature, a negative indication is sent to the arbiter 204 from any PDL analyzing unit that identifies PDLs solely on the basis of a signature. As the process proceeds to step 214, the nonsignature based PDL analyzing units scan the print job stream for either a single operator or sets of operators. After scanning a print job stream, with operators, for a selected interval, a distribution indicating the frequency of occurrence of one operator or selected sets of operators can be developed by at least one of the PDL analyzing units which recognizes a PDL on the basis of operator content. Referring to Figure 8, a sample distribution for one of the operator-based units is shown. In this sample distribution, one set of operators corresponds with the maximum of the distribution curve. Preferably a certainty factor, which corresponds to a specific PDL type or a specific PDL version type, is assigned in view of the operator set that is mapped with the distribution curve maximum. To demonstrate the manner in which this assignment technique functions, an example follows. In one example, the PDL may be one of three related types, namely PS Level 1, PS Level 2 or Binary PS Level 2. Assuming that only one PDL analyzing unit is provided to recognize all three related types, then one of four distinct certainty factors is assigned for the one unit. That is, a null factor is assigned when neither of the three related types is communicated to the one PDL analyzing unit and one of three certainty factors is assigned when one of the three related types is communicated to the one PDL analyzing unit. In another embodiment, a PDL analyzing unit would be provided for every conceivable PDL type or version to be analyzed by the PDL determining arrangement 200. In this embodiment, there would be no need to assign certainty factors. Rather, each PDL analyzing unit would simply indicate whether a particular PDL had passed through it or not. For the embodiment in which certainty factors are assigned, respective, corresponding information signals are generated, at step 218. In step 220, each of the information signals generated by the PDL analyzing units 202 are outputted from the PDL analyzing units 202, and, in step 224 the information signals are transmitted to the arbiter 204. Each of the signals are then arbitrated, conjunctively, with the arbiter 204 (step 224), the arbiter, in the preferred embodiment, including a set of rules. In one example the rules may be hard-coded, and in another example the rules may be programmed dynamically through use of a configuration file. Preferably, the configuration file assumes a hierarchical form of the type shown in EP-A-0,588,513. Since the configuration file is programmable, the arbiter can be altered readily in conformance with the needs of various clients. In one example, rules are dynamically reconfigured through use of the server rules line or the client server lines. That is, through use of of the rules lines a client user or a server administrator can display the current rules on an appropriate display, and selected rules can be deleted and replaced with other desired rules. Through use of the rules inputs, the client user or server administrator may set printing priorities and/or precedents. For example, the decomposer 96 (Figure 4) may be able to process Interpress IMG (i. e. a PDL written for Xerox® 4000 printer format) but not Interpress RES (i. e. a PDL compatible with Xerox® 6085 software, namely Viewpoint™). With this condition in mind, the server administrator may want to add a rule that permits a fault message to be transmitted to any particular client that may send a print job, written in Interpress RES, to the arrangement 70. Through use of over-ride signals, either the client user or the server administrator can direct arbiter operation to correspond with various existing conditions of the printing system. For example, the client may wish to print a particular PS job as noninterpreted text so that he can perform diagnostics on that particular print job. Under certain circumstances the printing system would interpret the particular PS job and produce prints therefrom. Through use of the client over-ride signal, the client can direct the server to bypass interpretation of the particular PS job so that the job is printed in noninterpreted text rather than PS. As mentioned above, one of the PDL analyzing units may include a binary filter, the binary filter being employed to collect statistics regarding the occurrence of binary characters in the print job stream. This prevents a data stream from fooling the arrangement 200 into reporting that a print job is written in PS when, for example, it happens to include an executable image that simply contains valid PS operators or keywords. The arbiter 204 uses the binary filter's knowledge of the print job stream to prevent it from reporting PS when the print job stream contains fewer than a selected percentage of binary characters. In one example the selected percentage is 50%. After the information signals have been arbitrated with the arbiter 204, the resulting arbitrated signal, indicating the PDL of the print job stream, is transmitted to the host processor 72. As discussed above, the host processor uses this information to insure that the appropriate PDL interpreter resides in the Accelerator Coprocessor (Figure 4). Numerous features of the present disclosed embodiment will be appreciated by those skilled in the art: One feature of the disclosed embodiment is efficient PDL analyzing of a print job stream. That is, a print job stream is scanned simultaneously by a plurality of PDL analyzing units, and each of the units is able to provide information simultaneously about the PDL type embodied by the stream. Moreover, the PDL analyzing units can provide information regarding the presence of a PDL version type in the print job stream. Another feature of the disclosed embodiment is flexibility and extentability. That is, PDL analyzing units can be added and deleted as desired in a modular fashion. To accommodate for such addition(s) or deletion(s) an arbiter, which is used to filter the outputs of the PDL analyzing units, can be provided with a programmable, configuration file. Yet another feature of the disclosed embodiment is tunability of the arbiter. The arbiter communicates with various inputs, which inputs can be used to program the arbiter dynamically. Moreover, the inputs permit the arbiter to be over-ridden by either a client user or a server administrator.

Claims: A printing system for producing prints from a print job written in one of a plurality of page description languages with the print job assuming a form of a print job stream, the system comprising: an input source for generating the print job and transmitting the print job stream; a plurality of page description language analyzing units (202) for sampling the print job stream, each analyzing unit (202) outputting an information signal which provides information regarding the print job stream; and a filter (204), receiving each of the information signals, for processing the information signals and outputting a filtered signal which indicates the page description language in which the print job is written; characterized in that said filter (204) is programmable and includes criteria for the processing of the information signals, and said input source includes means for over-riding one of the criteria. A printing system as claimed in claim 1, further comprising a print server (25) for interpreting the page description language of the print job to prepare the print job for printing, and wherein said server (25) includes means for over-riding one of the criteria. A printing system as claimed in claim 1 or 2, in which the print job stream includes an operator representative of the page description language in which the print job is written, wherein one of the information signals indicates the presence of the representative operator in the image data stream. A printing system as claimed in claim 1 or 2, in which the print job stream includes a plurality of operators representative of the page description language in which the print job is written and sets of selected operators follow a distribution, wherein a certainty factor, varying as a function of the distribution, is outputted from one of said page description language analyzing units (202). A printing system as claimed in claim 1 or 2, in which the page description language of the print job possesses a characteristic signature recognized by one of said page description language analyzing units (202), wherein said one of said page description language analyzing units (202) translates the characteristic signature into one of the information signals. A printing system as claimed in any one of the preceding claims, further comprising a binary filter, sampling the print job stream and communicating with said filter, for providing said filter with an indication of the percentage of binary characters in the print job to prevent erroneously indicating that the print job is written predominantly in one page description language when it is written predominantly in another page description language. A method of determining a page description language of a print job, the print job being written in one of a plurality of page description languages and assuming a form of a print job stream, comprising the steps of: communicating (208) the print job stream to a plurality of page description language analyzing units; generating (218) a plurality of information signals from the plurality of page description language analyzing units, each of the information signals providing information regarding the print job stream; transmitting (222) the information signals to a filter; and processing (224) the information signals with the filter for generating a filtered signal that indicates the page description language in which the print job is written; characterized in that said processing step (224) includes processing the information signals with selected criteria, further comprising the step of transmitting a signal to the filter for over-riding one of the criteria. A method as claimed in claim 7, in which the selected criteria is part of a configuration file, further comprising the step of programming the configuration file. A method as claimed in claim 7 or 8, in which the page description language is characterized by an operator, wherein said generating step (218) includes providing one of the plurality of information signals with a certainty factor for indicating the frequency of occurrence of the operator in the print job. A method as claimed in claim 7 or 8, in which the page description language is one of a plurality of versions, further comprising the step of indicating, with the certainty factor, which one of the plurality of versions is present in the print job stream. A method as claimed in claim 7 or 8, in which the page description language is characterized by a signature, wherein said generating step includes indicating, with one of the information signals, the presence of the signature. A method as claimed in any one of claims 7 to 11, in which the print job includes a plurality of characters, further comprising the step of informing the filter of the percentage of binary characters in the print job so that the filter can determine accurately the page description language of the print job.

Inventors: BIGBY BRUCE W, BRINDLE EDWARD E, O'BRIEN MARK D, BIGBY, BRUCE W., BRINDLE, EDWARD E., O'BRIEN, MARK D.
Applicants: XEROX CORP, XEROX CORPORATION
Application year: 1994
Main classification: G06F3
IPC codes: B41J5, G06F3